alfalfa root nodules have the capability to fix atmospheric dinitrogen through symbiosis with the soil born bacteria Rhizobium meliloti. Many enzymes are involved in the assimilation of symbiotically fixed nitrogen. One is the NADH-dependent Glutamate Synthase (NADH-GOGAT) which forms two Glutamate out of Glutamine and a-oxoglutarate. The enzyme is thought to be the rate limiting step in this pathway. In order to understand the biochemistry of the nitrogen assimilation in root nodules, localization of NADH-GOGAT is crucial. We will high-pressure freeze samples of root nodules and then freeze substitute, embed and sectioned. Sections will be immunostained and examined in the TEM in order to localize NADH-GOGAT.